Compact Autonomous Coverage Robot

ABSTRACT

An autonomous coverage robot includes a chassis having forward and rearward portions and a drive system carried by the chassis. The forward portion of the chassis defines a substantially rectangular shape. The robot includes a cleaning assembly mounted on the forward portion of the chassis and a bin disposed adjacent the cleaning assembly and configured to receive debris agitated by the cleaning assembly. A bin cover is pivotally attached to a lower portion of the chassis and configured to rotate between a first, closed position providing closure of an opening defined by the bin and a second, open position providing access to the bin opening. The robot includes a body attached to the chassis and a handle disposed on an upper portion of the body. A bin cover release is actuatable from substantially near the handle.

CROSS REFERENCE TO RELATED APPLICATIONS

This U.S. patent application claims priority under 35 U.S.C. §119(e) toU.S. Provisional Application 60/938,699, filed on May 17, 2007 and U.S.Provisional Application 60/917,065, filed on May 9, 2007. Thedisclosures of the prior applications are considered part of thedisclosure of this application and are hereby incorporated by referencein their entireties.

The contents of U.S. Pre-grant Publications 2003/0192144, 2006/0200281,and 2007/0016328, and also U.S. Pat. Nos. 6,748,297 and 6,883,201 arehereby incorporated herein by reference in their entireties.

TECHNICAL FIELD

This disclosure relates to autonomous coverage robots for cleaningfloors or other surfaces.

BACKGROUND

Autonomous robots are robots which can perform desired tasks inunstructured environments without continuous human guidance. Many kindsof robots are autonomous to some degree. Different robots can beautonomous in different ways. An autonomous coverage robot traverses awork surface without continuous human guidance to perform one or moretasks. In the field of home, office and/or consumer-oriented robotics,mobile robots that perform household functions such as vacuum cleaning,floor washing, patrolling, lawn cutting and other such tasks have beenwidely adopted.

Mobile robots for cleaning floors have been described in, for example,U.S. Pat. No. 6,883,201 to JONES et al. (“JONES”), which discloses anautonomous floor-cleaning robot that traverses a floor while removingdebris using rotating brushes, vacuums, or other cleaning mechanisms.JONES further describes a robot having a generally round form factorsupported by three wheels, which can rotate freely to maneuver aroundobstacles, inter alia.

SUMMARY

Presently disclosed is a compact mobile robot for cleaning floors,countertops, and other related surfaces, such as tile, hardwood orcarpeted flooring. The robot has a rectangular front form factor thatfacilitates cleaning along wall edges or in corners. In one example, therobot includes both a rounded section and a rectangular section, inwhich a cleaning mechanism within the rectangular section is disposedproximally to opposite side corners of the rectangular section. As anadvantage, the robot can maneuver so as to bring the rectangular sectionflush with a wall corner or wall edge, with the cleaning mechanismextending into the wall corner or wall edge.

In one aspect, an autonomous coverage robot includes a chassis havingforward and rearward portions and a drive system carried by the chassis.The forward portion of the chassis defines a substantially rectangularshape. The robot includes a cleaning assembly mounted on the forwardportion of the chassis and a bin disposed adjacent the cleaningassembly. The bin is configured to receive debris agitated by thecleaning assembly. A bin cover is pivotally attached to a lower portionof the chassis and configured to rotate between a first, closed positionproviding closure of an opening defined by the bin and a second, openposition providing access to the bin opening. The robot includes a bodyattached to the chassis and a handle disposed on an upper portion of thebody. A bin cover release is configured to control movement of the bincover between its first and second positions. The bin cover release isactuatable from substantially near the handle.

Implementations of this aspect of the disclosure may include one or moreof the following features. In some implementations, the bin coverrelease is configured to move between a first, locking position whichlocks the bin cover in its first, closed position and a second,disengaged position which allows the bin cover to move to its second,open position. The bin cover release may be a spring biased latch. Insome examples, the bin cover release includes a button disposed on thehandle configured to actuate the latch, thereby allowing actuation ofthe bin cover release while holding the handle. In some implementations,the drive system includes right and left differentially driven drivewheels rotatably mounted to the rearward portion of the chassis. Thedrive system is capable of maneuvering the robot to pivot in place.

In another aspect, an autonomous coverage robot includes a chassishaving forward and rearward portions, and a drive system carried by therearward portion of the chassis. The drive system is configured tomaneuver the robot over a cleaning surface. The robot includes acontroller in communication with the drive system. The controller isconfigured to maneuver the robot to pivot in place. The robot includes acleaning assembly mounted on the forward portion of the chassis. Therobot includes a bump sensor in communication with the controller whichis configured to detect movement in multiple directions. A body isflexibly attached to the chassis and substantially covers the chassis.Contact with the body is translated to the bump sensor for detection.The controller is configured to alter a drive direction of the robot inresponse to a signal received from the bump sensor. The bump sensorincludes a sensor base, a sensor shroud positioned adjacent the sensorbase and connected to the body, an emitter housed by the sensor shroud,and at least three detectors carried by the sensor base. The emitteremits a signal onto the sensor base, and the detectors are configured todetect the emitted signal. Movement of the sensor shroud causes movementof the emitted signal over the detectors. In some implementations, therobot includes a bin disposed adjacent the cleaning assembly andconfigured to receive debris agitated by the cleaning assembly.

Implementations of this aspect of the disclosure may include one or moreof the following features. In some implementations, the bump sensordetects 360 degrees of movement of the body about the bump sensor.Preferably, the bump sensor includes four detectors arranged in arectangular configuration with respect to each other. The sensor shrouddefines an orifice through which the emitter emits its signal onto thesensor base. The emitter comprises an infrared light emitter and thedetectors comprise infrared light detectors, the orifice collimating theemitted signal onto the sensor base. In some examples, the robotincludes a bumper guide configured to confine body movements to alongtwo directions. The bumper guide may include two orthogonal groovesdefined by the body and configured to receive a guide pin disposed onthe chassis. The forward portion defines a substantially rectangularshape, in some examples. The drive system, in some examples, includesright and left drive wheels differentially driven by corresponding rightand left motors.

In yet another aspect, an autonomous coverage robot includes a chassishaving forward and rearward portions, and a drive system carried by therearward portion of the chassis. The forward portion defines asubstantially rectangular shape and the rearward portion of the chassisdefines an arcuate shape. The drive system is configured to maneuver therobot over a cleaning surface and includes right and left drive wheelsdifferentially driven by corresponding right and left motors. The robotincludes a controller in communication with the drive system. Thecontroller is configured to maneuver the robot to pivot in place. Therobot includes a cleaning assembly mounted on the forward portion of thechassis. The robot includes an accelerometer in communication with thecontroller, which controls the drive system in response to a signalreceived from the accelerometer. In some implementations, the robotincludes a bin disposed adjacent the cleaning assembly and configured toreceive debris agitated by the cleaning assembly.

Implementations of this aspect of the disclosure may include one or moreof the following features. In some implementations, the controlleralters a drive direction of the robot in response to a signal receivedfrom the accelerometer indicating an abrupt speed change. The controlleralters a drive direction of the robot in response to a signal receivedfrom the accelerometer indicating stasis of the robot. The controllerreduces a drive speed of the robot in response to a signal received fromthe accelerometer indicating a maximum speed. In some examples, themaximum speed is between about 200 mm/s and about 400 mm/s.

Implementations of the above aspects of the disclosure may include oneor more of the following features. In some implementations, the cleaningassembly includes a first roller brush rotatably mounted substantiallynear a front edge of the chassis. The cleaning assembly may include asecond roller brush rotatably mounted substantially parallel to andrearward of the first roller brush, the first and second roller brushesrotate in opposite directions. The bin is disposed rearward of the firstand second roller brushes and forward of the drive system. Each rollerbrush includes right and left end brushes extending from respective endsof the roller brush beyond a lateral extend of the body, each end brushextending at angle φ of between 0° and about 90° from a longitudinalaxis defined by the roller brush. In other implementations, the cleaningassembly includes a front roller brush rotatably mounted substantiallynear the front edge of the chassis, and right and left side rollerbrushes rotatably mounted orthogonal to the front brush substantiallynear the respective right and left side edges of the chassis. The bin isdisposed rearward of the front roller brush and substantially betweenthe right and left side roller brushes and forward of the drive system.

In another aspect, an autonomous coverage robot includes a chassishaving forward and rearward portions, and a drive system carried by therearward portion of the chassis. The forward portion defines asubstantially rectangular shape and the rearward portion defines anarcuate shape. The drive system is configured to maneuver the robot overa cleaning surface and includes right and left drive wheelsdifferentially driven by corresponding right and left motors. The robotincludes a controller in communication with the drive system. Thecontroller is configured to maneuver the robot to pivot in place. Therobot includes a cleaning assembly mounted on the forward portion of thechassis and includes a first roller brush rotatably mountedsubstantially near a front edge of the chassis and a second roller brushrotatably mounted substantially parallel to and rearward of the firstroller brush. The first and second roller brushes rotate in oppositedirections. A bin is disposed rearward of the cleaning assembly and isconfigured to receive debris agitated by the cleaning assembly. A bincover is pivotally attached to a lower portion of the chassis and isconfigured to rotate between a first, closed position providing closureof an opening defined by the bin and a second, open position providingaccess to the bin opening. The robot includes a bin cover releaseconfigured to control movement of the bin cover between its first andsecond positions. A handle is disposed on the chassis. The bin coverrelease is actuatable from substantially near the handle. A body isflexibly attached to the chassis and substantially covers the chassis.The body is movable in relation to the handle and the chassis. The robotincludes a bump sensor in communication with the controller andconfigured to detect movement in multiple directions. Contact with thebody is translated to the bump sensor for detection. The controller isconfigured to alter a drive direction of the robot in response to asignal received from the bump sensor.

Implementations of this aspect of the disclosure may include one or moreof the following features. In some implementations, the bump sensorincludes a sensor base, a sensor shroud positioned adjacent the sensorbase and connected to the body, an emitter housed by the sensor shroud,and at least three detectors carried by the sensor base. The emitteremits a signal onto the sensor base and the detectors detect the emittedsignal. Movement of the sensor shroud causes movement of the emittedsignal over the detectors.

In some implementations, the robot includes a bumper guide configured toconfine body movements to along two directions. The bumper guide mayinclude two orthogonal grooves defined by the body and configured toreceive a guide pin disposed on the chassis.

The robot may include an idler wheel disposed on the bin cover. In someexamples, the rearward portion of the chassis defines a substantiallysemi-circular shape and the idler wheel is position at least ⅓ theradius of the substantially semi-circular shaped rearward portionforward of the drive wheels.

In specific examples, the drive wheels are disposed less than 9 cmrearward of the cleaning assembly. The robot may include a power sourcedisposed in the rearward portion of the chassis substantially betweenthe right and left wheels. The power source is disposed adjacent andrearward of the bin. The cleaning assembly further comprises a brushmotor configured to drive the first and second roller brushes. In someexamples, the brush motor is disposed substantially near a forward edgeof the chassis. The first roller brush may be disposed substantiallynear a forward edge of the chassis.

Implementations of the disclosure may include one or more of thefollowing features. In some implementations, the right and left drivewheels are rotatably mounted to the rearward portion of the chassis, andthe drive system is capable of maneuvering the robot to pivot in place.Preferably, the rearward portion of the chassis defines an arcuateshape; however other shapes are possible as well, such as rectangular orpolygonal. In some examples, the rearward portion of the chassis definesa substantially semi-circular shape and the axes of the right and leftdrive wheels are disposed on or rearward of a center axis defined by therearward portion of the chassis. In some implementations, the chassisand the body together have a length of less than 23 cm and a width ofless than 19 cm.

In some implementations, the robot includes at least one proximitysensor carried by a dominant side of the robot. The at least oneproximity sensor responds to an obstacle substantially near the body.The controller alters a drive direction in response to a signal receivedfrom the at least one proximity sensor.

In some implementations, the robot includes at least one cliff sensorcarried by a forward portion of the body and arranged substantially neara front edge of the body. The at least one cliff sensor responds to apotential cliff forward of the robot. The drive system alters a drivedirection in response to a signal received from the cliff sensorindicating a potential cliff. In some examples, right and left frontcliff sensors are disposed at the respective right and left corners of aforward portion of the robot. This allows the robot to detect when aeither of the front corners swing over a cliff edge, so as to avoidmoving the drive wheels any closer to the cliff edge. In someimplementations, the robot includes at least one cliff sensor carried bya rearward portion of the body and arranged substantially near the rearedge of the body. The at least one cliff sensor responds to a potentialcliff rearward of the robot. The drive system alters a drive directionin response to a signal received from the cliff sensor indicating apotential cliff. In some examples, right and left rear cliff sensors aredisposed directly rearward of the respective right and left drivewheels. This allow the robot to detect a cliff edge while driving inreverse at an angle or in an arc, in which the drive wheel may encounterthe cliff edge before the rear center portion of the robot.

In some implementations, the robot includes an idler wheel disposed onthe bin cover. Preferably, the rearward portion of the chassis defines asubstantially semi-circular shape, which allows the robot to spin inplace without catching any portion of the rearward portion of thechassis on a detected obstacle. The idler wheel is position at least ⅓the radius of the substantially semi-circular shaped rearward portionforward of the drive wheels. In some examples, the idler wheel is astasis detector including a magnet disposed in or on the idler wheel,and a magnet detector disposed adjacent the wheel for detecting themagnet as the idler wheel rotates.

In other more general aspects that are combinable with any of the aboveimplementations, an autonomous coverage robot includes a chassis and adrive system carried by the chassis. The drive system is configured tomaneuver the robot over a cleaning surface. In some examples, the drivesystem includes right and left differentially driven drive wheels;however other means of driving the robot are applicable as well, such asskid steer tracks. In some examples, the chassis has forward andrearward portions with the forward portion defining a substantiallyrectangular shape. Optionally, the rearward portion can define anarcuate shape.

In some implementations, the robot includes a cleaning assembly mountedon the forward portion of the chassis (e.g. substantially near a forwardedge of the chassis). A bin is disposed adjacent the cleaning assemblyand configured to receive debris agitated by the cleaning assembly. Insome examples, a bin cover is pivotally attached to the robot and isconfigured to rotate between a first, closed position providing closureof an opening defined by the bin and a second, open position providingaccess to the bin opening. In other examples, the bin cover is slidablyattached to the robot and slides between the first, closed position andthe second, open position.

In some implementations, a body is attached to the chassis. The body mayconform to the profile of the chassis. In some examples, the body isflexibly or movably attached to the chassis. The robot may include ahandle for carrying the robot. The handle can be disposed on the body oron the chassis. If the handle is disposed on the chassis, the body isallowed to move in relation to the handle and/or the chassis. The robotmay include a bin cover release configured to control movement of thebin cover between its first and second positions. Preferably, the bincover release is actuatable from substantially near the handle. However,the bin cover release may be actuatable from substantially near or onthe bin cover.

In some implementations, the robot includes a bump sensor, which may beconfigured to detect movement in multiple directions. In some examples,contact with the body is translated to the bump sensor for detection.The robot may include a controller configured to alter a drive directionof the robot in response to a signal received from the bump sensor. Insome examples, the robot includes an accelerometer in communication withthe controller, such that the controller controls the drive system inresponse to a signal received from the accelerometer.

The details of one or more implementations of the disclosure are setforth in the accompanying drawings and the description below. Otherfeatures, objects, and advantages will be apparent from the descriptionand drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a top perspective view of a compact autonomous coverage robot.

FIG. 2 is a bottom perspective view of the robot shown in FIG. 1.

FIG. 3 is a top view of the robot shown in FIG. 1.

FIG. 4 is a bottom view of the robot shown in FIG. 1.

FIG. 5 is an exploded view of the top aspect shown in FIG. 1.

FIG. 6 is a front view of the robot shown in FIG. 1.

FIG. 7 is a rear view of the robot shown in FIG. 1.

FIG. 8 is a left side view of the robot shown in FIG. 1 with a bin coverin its open position.

FIG. 9 is right side view of the robot shown in FIG. 1.

FIG. 10 is top perspective view of a compact autonomous coverage robot.

FIG. 11A is a side view of a stasis detector.

FIG. 11B is a top schematic view of a compact autonomous coverage robot.

FIG. 11C is a side schematic view of a compact autonomous coveragerobot.

FIG. 12A is a top view of a compact autonomous coverage robot scrapingalong a wall.

FIG. 12B is a top view of a compact autonomous coverage robot bumping awall.

FIG. 13A is a top schematic view of a compact autonomous coverage robotwith a bumper guide.

FIG. 13B is a side section view of a bump sensor.

FIG. 13C is a top schematic view of a bump sensor system with a bumperguide.

FIG. 13D is a perspective view of a bump sensor system.

FIG. 14 is a contour shaded diagram of the view of the compact cleaningrobot shown in FIG. 3.

FIG. 15 is a perspective exploded view of an omni-directional sensor.

FIG. 16 is a side view of the omni-directional sensor shown in FIG. 15.

FIG. 17 is a top perspective view of a compact autonomous coveragerobot.

FIG. 18 is a bottom perspective view of the robot shown in FIG. 17.

FIG. 19 is a top view of the robot shown in FIG. 17.

FIG. 20 is a bottom view of the robot shown in FIG. 17.

FIG. 21 is an exploded view of the top aspect shown in FIG. 17.

FIG. 22 is a front view of the robot shown in FIG. 17.

FIG. 23 is a rear view of the robot shown in FIG. 17.

FIG. 24 is a left side view of the robot shown in FIG. 17 with a bincover in its open position.

FIG. 25 is right side view of the robot shown in FIG. 17.

FIG. 26 is an oblique view of a compact cleaning robot havingrectangular form traversing along a wall edge.

FIG. 27 is a plan view of a compact cleaning robot navigating flush intoa wall corner.

FIG. 28 is a plan view of a round robot navigating into a wall corner,illustrating a gap that the round robot cannot traverse.

FIG. 29-32 collectively provide a schematic view of a control circuitfor an autonomous coverage robot.

FIG. 33 is a schematic view of a software architecture for a behavioralsystem of autonomous coverage robot.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring to FIGS. 1-3, an autonomous coverage robot 100 includes achassis 200 having a forward portion 210 and a rearward portion 220. Theforward portion 210 of the chassis 200 defines a substantiallyrectangular shape. In the example shown, the rearward portion 220 of thechassis 200 defines an arcuate shape (e.g., in the example shown therearward portion 220 is rounded); however, the rearward portion 220 maydefine other shapes as well, such as, but not limited to, rectangular,triangular, pointed, or wavy shapes.

Referring to FIGS. 1 and 5, the robot 100 includes a body 300 configuredto substantially follow the contours of the chassis 200. The body 300may be flexibly connected to the chassis 200 (e.g., by a spring orelastic element), so as to move over the chassis 200. In some examples,a handle 330 is disposed on or defined by an upper portion of the body300. In other examples, the handle 330 is secured to or extends from amounting piece 332, which is secured to an upper portion 205 of thechassis 200. The mounting piece 332 can be removable and interchangeablewith other mounting pieces 332 that have different arrangements or carryother components (e.g., different handles 330 and/or sensors). The body300 moves with respect to the mounting piece 332 and the chassis 200. Inthe example shown, the body 300 floats below the mounting piece 332. Themounting piece 332 can by circular and sized to be offset from arespective opening defined by an upper portion (305) of the body 300, soas to provide a 360° displacement limit for body movement (e.g., 2-4 mmof bumper movement) due to contact with the body (e.g., along a lowerportion 303 of the body 300 (see FIG. 8). The robot 100 (including thechassis 200 and the body 300) has a compact footprint with a length ofless than 23 cm and a width of less than 19 cm.

Referring to FIGS. 4 and 5, the robot 100 includes a drive system 400carried by the chassis 200 and configured to maneuver the robot 100 overa cleaning surface. In the example shown, the drive system 400 includesright and left drive wheels 410 and 420, respectively, which aredifferentially driven by corresponding right and left drive motors 412and 422, respectively. The drive motors 412, 422 are mounted above theirrespective drive wheels 410, 420, in the example shown, to help maintainthe compact footprint of the robot 100. However, other implementationsinclude having the drive motors 412, 422 mounted adjacent (e.g.,co-axially with) their respective drive wheels 410, 420. In someexamples, the robot includes a gear box 414, 424 coupled between thedrive wheel 410, 420 and its respective drive motor 412, 422. The gearboxes 414, 424 and the drive motors 412, 422 are configured to propelthe robot at a maximum velocity of between about 200 mm/s and about 400mm/s (preferably 306 mm/s) and a maximum acceleration of about 500mm/s². In some implementations, the center axles of the drive wheels410, 420 are disposed less than 9 cm (preferably 8 cm) rearward of acleaning assembly 500, which will be described below. The robot 100includes a controller 450 in communication with the drive system 400.The controller 450 is configured to maneuver the robot 100 to pivot inplace.

The advantage of the conventional cylindrical robot with drives wheelsdisposed on the diameter of the robot is that it is not hindered fromturning in the presence of obstacles. This enables a simple andeffective escape strategy-spin in place until no objects are detectedforward of the robot. If the robot is non-cylindrical or the axes ofwheel rotation are not on a diameter of the robot then the normal andtangential forces on the robot change as the robot rotates while incontact with an object. To ensure that such a non-conventional robot isable to escape an arbitrary collision, the forces and torques applied tothe robot by the environmental cannot combine with the robot-generatedforces and torques to halt robot motion. In practice this means that therobot shape should be constant width (to within the shell compliancedistance) and that the robot's wheels be capable of lateral motion.Particular shapes then yield different requirements for maximum lateralwheel forces and maximum allowable environmental coefficient offriction. However, the robot 100 presently disclosed, in some examples,has a rectangular forward portion 210 to allow cleaning fully intocorners.

Referring again to the example shown in FIG. 4, a profile circle 221defining the substantially semi-circular profile of the rearward portion220 of the chassis 200 extends into the forward portion 210 of thechassis 200 and has a center axis 223. The drive wheels 410, 420 arepositioned on or substantially near the center axis 223 of the profilecircle 221. In the example shown, the drive wheels 410, 420 arepositioned slightly rearward of the center axis 223 of the profilecircle 221. By positioning the drive wheels 410, 420 on or rearward ofthe center axis 223 of the profile circle 221, the robot 100 can turn inplace without catching rearward portion 220 of the chassis 200 on anobstacle.

Referring to FIGS. 2, 4 and 5-9, the robot 100 includes a cleaningassembly 500 mounted on the front portion 210 of the chassis 200substantially near a front edge 202 of the chassis 200. In the examplesshown, the cleaning assembly 500 includes first and second rollerbrushes 510, 520 rotatably mounted substantially parallel to each other.The roller brushes 510, 520 are driven by a cleaning motor 530 coupledto a middle portion of the roller brushes 510, 520 by a gear box 532.The cleaning motor 530 is positioned above the roller brushes 510, 520to confine the cleaning assembly 500 to the forward portion 210 of thechassis 200 and to help maintain a compact robot with a relatively smallfootprint. Each roller brush 510, 520 may include an end brush 540disposed at each longitudinal end 512, 514, 522, 524 of the roller brush510, 520. Each end brush 540 is disposed at an angle φ with alongitudinal axis 513, 523 defined by the roller brush 510, 520 ofbetween 0° and about 90° (preferably 45°). The end brush 540 extendsbeyond the chassis 200 and the body 300 (e.g., beyond respective rightand left side edges 306, 308) to agitate debris on or along objectsadjacent the robot 100 (e.g., to clean up against walls). Otherimplementations of the cleaning assembly 500 will be discussed laterwith reference to another implementation of the robot 100.

Referring to FIGS. 1-5, 8, and 10, the robot 100 includes a bin assembly600 disposed adjacent the cleaning assembly 500 and configured toreceive debris agitated by the cleaning assembly 500. In some examples,the chassis 200 defines a debris chamber or bin 610 (see FIG. 10). Inother examples, a bin 610 is disposed below the chassis and positionedto receive debris agitated by the cleaning assembly 500. In the examplesshown, the bin 610 is positioned substantially between the cleaningassembly 500 and the drive system 400. Specifically, the bin 610 isforward of the drive wheels 410, 420 and rearward of the roller brushes510, 520.

Preferably, the debris chamber/bin 610 is defined by, and thus formedintegrally with, the chassis 200. In an alternative configuration, therobot 101 may include a modular, removable cartridge or bag serving asthe debris chamber/bin 610, such that the user can remove the debris byremoving and emptying the cartridge or bag. The cartridge or bag 610 isremovably secured to the chassis 200.

A bin cover 620 is pivotally attached to a lower portion 203 of thechassis 200 and configured to rotate between a first, closed positionproviding closure of an opening 612 defined by the bin 610 and a second,open position providing access to the bin opening 610. In some examples,the bin cover 620 is releasably connected to the chassis 200 by one ormore hinges 622. The bin assembly 600 includes a bin-cover release 630configured to control movement of the bin cover 620 between its firstand second positions. The bin-cover release 630 is configured to movebetween a first, locking position which locks the bin cover 620 in itsfirst, closed position and a second, disengaged position which allowsthe bin cover 620 to move to its second, open position (see FIG. 8). Thebin-cover release 630 is actuatable from substantially near or at thehandle 330, thereby allowing actuation of the bin-cover release 630while holding the handle 330. This allows a user to pick up the robot100 via the handle 330 with one hand, hold the robot 100 over a trashbin (not shown), and actuate the bin-cover release 630 with the samehand holding the handle 330 to release the bin cover 620 and empty thecontents of the bin 610 into the trash bin. In some implementations, thebin cover release 630 is a spring biased latch or latching buttonattractable by pressing downwardly (e.g., button) or pulling upwardly(e.g., trigger).

The robot 100 includes a power source 160 (e.g., battery) incommunication with the drive system 400 and/or the controller 450, andremovably secured to the chassis 200. In the examples shown in FIGS. 2,4, 5, and 7-8, the power source 160 is received by a power receptacle260 defined by the rearward portion 220 of the chassis 200. In someexamples, the power source 160 is positioned substantially under thecontroller 450 and between the right and left drive wheels 410, 420,while extending forward to a distance sufficient to place a center ofgravity of the robot 100 substantially at the center of the chassis 200or substantially between a first transverse axis 415 defined by thedrive wheels 410, 420 and a second transverse axis 425 defined by afree-wheel 722 (e.g., stasis wheel 722) (see FIG. 4). If the weight ofthe power source 160 is positioned too far rearward, there will not beenough weight over the cleaning assembly 500, allowing the forwardportion 210 of the chassis 200 to tip upward. As being a compact robot100 with a relatively small footprint, the arrangement of components onand within the chassis 200 is important to achieve the compact size ofthe robot 100 while remaining functional. Referring to FIGS. 5 and 8,the debris chamber/bin 610 impedes the forward placement of the powersource 160 (e.g., the power source 160 is limited to positioning in therearward portion 210 of the chassis 200). Nevertheless, the power source160 is positioned between the drive wheels 410, 420 and as far forwardas possible, substantially abutting the bin 610, so as to place thecenter of gravity of the robot forward of the first transverse axis 415defined by the drive wheels 410, 420. By placing the center of gravityforward of the drive wheels 410, 420, the robot 100 is less likely totip up and backwards (e.g., when going over thresholds).

Referring to FIGS. 1-11, the robot 100 includes a navigational sensorsystem 700 in communication with the controller 450 that allows therobot 100 to be aware of its surroundings/environment and react inprescribed manners or behaviors according to its sensed perception ofits surroundings/environment. A description of behavior control can befound in detail in Jones, Flyun & Seiger, Mobile Robots: Inspiration toImplementation second edition, 1999, A K Peters, Ltd., the text of whichis hereby incorporated by reference in its entirety. The navigationalsensor system 700 includes one or more cliff sensors 710, a stasisdetector 720, a proximity sensor 730, at least one bump sensor 800,and/or an omni-directional receiver 900. Using input from thenavigational sensor system 700, the controller 450 generates commands tobe carried out by the robot 100. As a result, the robot 100 is capableof cleaning surfaces in an autonomous fashion.

The cliff sensors 710 may be used to sense when the robot 100 hasencountered the edge of the floor or work surface, such as when itencounters a set of stairs. The robot 100 may have behaviors that causeit to take an action, such as changing its direction of travel, when anedge is detected. In the examples shown in FIGS. 2, 4, 5, and 10, thebody 300 of the robot 100 houses four cliff sensors 710 along aperimeter of the body 300, with two cliff sensors 710 substantiallyalong a front edge 302 of a forward portion 310 of the body 300(preferably near forward outer corners or lateral edges) and two cliffsensors 710 substantially along a rearward edge 304 of a rearwardportion 320 of the body 300 (preferably near rearward outer corners orlateral edges) (see FIG. 4). Each cliff sensor 710 includes an emitter712 that sends a signal and a receiver 714 configured to detect areflected signal. In some implementations, cliff sensors 1074 may beinstalled within a mounting apparatus that stabilizes and protects thesensor and which positions the sensor to point towards the windowinstalled onto the bottom of the mounting apparatus. Together thesensor, the mounting apparatus and the window comprise a cliff sensorunit. Reliability of the cliff sensor 710 may be increased by reducingdust buildup. In some implementations, a window may be installed on thebottom of the mounting apparatus which includes a shield mounted withina slanted molding composed of a material which prevents dust build up,such as an antistatic material. The shield component and the molding maybe welded together. To further facilitate the reduction in dust and dirtbuildup, the shield may be mounted on a slant to allow dirt to moreeasily slide off. In some implementations, a secondary cliff sensor 710may be present behind existing cliff sensors 710 to detect floor edgesin the event that a primary cliff sensor 710 fails.

Robots defining shapes of constant width can turn in place about theircentroid locus of the respective shape. A shape of constant width is aconvex planar shape whose width, measured by the distance between twoopposite parallel lines touching its boundary, is the same regardless ofthe direction of those two parallel lines.

The width of the shape in a given direction is defined as theperpendicular distance between the parallels perpendicular to thatdirection. The Reuleaux triangle is the simplest example (after thecircle) of shapes of constant width. However, in the examples shown, therobot 100 has a rectangular shaped forward portion 210 of the chassis200, and thus not a robot of constant width, which can prevent the robotfrom spinning in place to escape from various stuck positions, such aswith canyoning situations, inter alia. Canyoning situations arise whenthe robot 100 drives down a narrow corridor (with side walls) or plank(with side cliffs) that is slightly wider than the robot 100. When therobot 100 reaches the end of the corridor or plank it can only escape bydriving in reverse back out of the corridor or off of the plank. If therobot 100 tries to spin in place (e.g., to rotate 180°) one of therobot's corners will hit a wall or go off a cliff. In the case ofcliffs, the placement of cliff sensors 710 substantially along arearward edge 304 of the body 300 or a rearward edge 204 of the chassis200 allows the robot 100 to backup intelligently to escape withoutbacking off a cliff. Similarly, the bump sensor 800, which will bedescribed below, detects reward bumps, allowing the robot 100 to backout of narrow corridors.

Referring to FIGS. 2, 4, 5 and 11A, the stasis detector 720 indicateswhen the robot 100 is moving or stationary. In the examples shown, thestasis detector 720 includes a stasis wheel 722 with a magnet 724 eitherembedded in or disposed on the wheel 722. A magnetic receiver 726 (e.g.,inductor) is position adjacent the wheel 722 to detect the magnet 724moving past. The magnetic receiver 726 provides an output signal to thecontroller 450 that indicates when the magnet 724 moves past themagnetic receiver 726. The controller 450 can be configured to determinehow fast and far the robot 100 is traveling based on the output signalof the magnetic receiver 726 and the circumference of the stasis wheel722. In other implementations, the stasis detector 720 includes a stasiswheel 722 with circumferential surface having at least two differentreflective characteristics (e.g., white and black). A stasis emitter andreceiver pair (e.g., infrared) is disposed adjacent the stasis wheel722. The stasis emitter is configured to emit a signal onto thecircumferential surface of the stasis wheel 722, and the stasis receiveris configured to detect or receive a reflected signal off of thecircumferential surface of the stasis wheel 722. The stasis detector 720monitors the transitions between reflection states and non-reflectionstates to determine if the robot 100 is moving, and perhaps even therate of movement.

Again due to the compact nature of the robot 100 and the compactpositioning of components, the stasis wheel 722 acts as a third wheelfor stable ground contact. If the stasis wheel 722 was placed forward ofthe cleaning assembly 500, it would need to be a caster wheel, ratherthan a directional wheel, which would drag in an arc when the robot 100turns. However, the need for a rectangular forward portion 210 of thechassis 200, so as to fully clean in corners, prohibits placement of thestasis wheel 722 forward of the cleaning assembly 500 (e.g., which wouldresult in a shape other than rectangular). A wheel is needed forward ofthe drive wheels 410, 420 to lift the forward portion 210 of the chassis200 to an appropriate height for cleaning and brush rotation.

Referring to again FIG. 4, the stasis wheel 722 is disposed in the bincover 620, just rearward of the cleaning assembly 500 and forward of thedrive system 400 and the power source 160. The stasis/idler wheel 722 ispositioned forward of the drive wheels 410, 420, forward of the centeraxis 223 of the profile circle 221, and within the profile circle 221.This positioning of the stasis wheel 722 allows the robot 100 to turn inplace without substantially dragging the stasis wheel 722 across itsrolling direction, while also providing support and stability to theforward portion 210 of the chassis 200. Preferably, the stasis wheel 722is positioned at least ⅓ the radius of the center axis 223. The forwardpositioning of the stasis wheel 722 and the power source 160 isobstructed by the cleaning assembly 500. As a result, decreasing thesize of the cleaning assembly 500 would allow further forward placementof the stasis wheel 722 and the power source 160 or a decrease in theoverall length of the robot 100.

The examples shown in FIGS. 11B-11C illustrate the placement ofcomponents in the robot 100 to achieve a compact morphology as well asstability for movement. Where LD=flat cliff detector 710A, 710Bthickness, CH=cleaning head 500 front-to-back length, WB=wheelbase,RD=angled cliff detector 710C, 710D front to back length, WT=WheelTrack, and CR=circular radius (>½ wheel track), the tombstone shapedrobot 100 has a length that is: 1) greater than LD+CH+WB+CR and 2) Equalto or less than 1.4 CR, where 3) RD<½ CR, WB>⅓ CR, CG is within WB. Theplacement of the components to satisfy the above relationship places thecenter of gravity 105 of the robot forward of the drive wheels 410, 420and within the circular radius CR. The figures also illustrate theplacement of two of the heaviest components, which include the powersource 160 having a center of gravity 165 and the brush motor 515 havinga center of gravity 517. The brush motor 515 is positioned as farforward as possible to place its center of gravity 517 as far forward aspossible, so as to offset the weight of the power source 160. Similarly,the power source 160 is positioned as far forward as possible to placeits center of gravity 165 as far forward as possible as well. However,forward placement of the power source 160 is generally obstructed by thecleaning assembly 500 and the bin 610.

Referring to FIGS. 1, 5 and 9, the proximity sensor 730 may be used todetermine when an obstacle is close to or proximate the robot 100. Theproximity sensor 730 may, for example, be an infrared light orultrasonic sensor that provides a signal when an object is within agiven range of the robot 100. In the examples shown, the proximitysensor 730 is disposed on a side (e.g., right side) of the robot 100 fordetecting when an object, such as a wall, is proximate that side.

In a preferred implementation, as shown, the side of the robot 100having the proximity sensor 730 is the dominant side of the robot 100,which in this case is the right-hand side relative to a primarydirection of travel 105. In some examples, the wall proximity sensor 730is an infrared light sensor composed of an emitter and detector paircollimated so that a finite volume of intersection occurs at theexpected position of a wall. This focus point is approximately threeinches ahead of the drive wheels 410, 420 in the direction of robotforward motion. The radial range of wall detection is about 0.75 inches.The proximity sensor 730 may be used to execute wall followingbehaviors, examples of which are described in U.S. Pat. No. 6,809,490,the entire contents of which is hereby incorporated by reference in itsentirety.

In some implementation, the proximity sensor 730 includes an emitter anda detector disposed substantially parallel. The emitter has an emissionfield projected substantially parallel to a detection field of thedetector. The proximity sensor 730 provides a signal to the controller450, which determines a distance to a detected object (e.g., a wall).The proximity sensor 730 needs to be calibrated to accurately detect andallow the controller 450 to determine an object distance. To calibratethe proximity sensor 730 to the albedo (e.g., color or reflectivity) ofan adjacent object, the robot 100 bumps into the object on its dominantside and records a reflection characteristic. In the example of aninfrared emitter and detector, the controller 450 records a reflectionintensity at the moment of contact with the object, which is assumed tobe a wall. Based on the recorded reflection intensity at the knowncalibration distance between the edge of the body 300 and the proximitysensor 730, the controller 450 can determine a distance to the wallthereafter while driving alongside the wall. The controller 450 canimplement servo control on the drive motors 412, 422 to drive at acertain distance from the wall, and hence wall follow. The robot 100 mayperiodically turn into the wall to side-bump the wall and re-calibratethe proximity sensor 730. If the proximity sensor 730 senses an absenceof the wall, the robot 100 may decide to re-calibrate the proximitysensor 730 upon recognition of the wall again.

The robot 100 can actively wall follow on its dominant side by using theproximity sensor 730. The robot 100 can passively wall follow on itsnon-dominant side (or the dominant side if the proximity sensor 730 isnot present or active). After bumping into an object (e.g., sensed bythe bump sensor 800), the robot 100 can assume that the object is a walland turn to follow the wall. The robot 100 may back-up before turning,so as to not catch a front corner of the body 300 on the object/wall,thus re-triggering the bump sensor 800 in a forward direction. Afterturning (e.g., about 90°), the robot 100 drives straight (e.g., alongthe wall) and slightly turns into the wall, so as to scrape along thewall. The robot 100 can sense that it's scraping along the wall bydetecting a side-bump via the multi-directional bump sensor 800, whichwill be described below. The robot 100 can continue to passively wallfollow until the bump sensor 800 no longer detects a side-bump on thecurrent wall-following side of the robot 100 for a certain period oftime.

The robot 100 can passively wall follow due in-part to its flat sides ofthe body 300 and the rear placement of the drive wheels 410, 420. Theflat sides allow the robot 100 to scrape along the wall (e.g.,substantially parallel to the wall). The positioning of the drive wheels410, 420 in the rear portion 220 of the chassis 200 allows the robot 100to swing its forward portion 210 of the chassis 200 into the wall, so asto scrape along the wall. Referring to FIG. 12A, the robot 100 movingforward while in contact with a wall 30 is subject to two forces—a forcenormal to the wall, F_(n), and a force tangential to the wall, F_(t).These forces create opposing torques about a point midway between thewheels, the natural center of rotation of the robot. It can be shownthat the torque, τ, is:

τ=rF(cos θ sin θ−μ sin² θ)

Where μ is the coefficient of friction between the wall and the robot.Given a value for μ there is some critical angle θ_(c) where the torquesare balanced. For θ<θ_(c) the first term to the right in the equation islarger and the robot tends to align with the wall. If θ>θ_(c) then thesecond term is larger and the robot 100 tends to turn into the wall.

Certain robot geometries, such as the tombstone shape of the robotdisclosed can achieve useful values for θ_(c). Note that the standardcylindrical geometry has θ_(c)=π/2 regardless of the robot's approachangle to the wall. Thus, passive wall following cannot be achieved withthis configuration. To successfully passively wall follow, the offsetbetween the natural axis of robot rotation and the contact point withthe wall should be as far forward as possible when robot motion isaligned with the wall. Also, the maximum wall step height that allowspassive recovery is an important consideration and is affected by robotshape.

In some examples, the robot 100 can semi-passively wall follow. Therobot 100 wall follows on its dominant side, which has the sideproximity sensor 730. After detecting an object, assumed to be a wall,by either the bump sensor 800 or the proximity sensor 730, the robot 100turns to align the dominant side of the robot 100 with the assumed wall.The robot 100 then proceeds to drive along the wall while turningslightly into the wall so as to scrape along the wall. The robot 160maintains contact with the wall by sensing contact with the wall via thebump sensor 800 or the proximity sensor 730 and the controller 450implements servo control or the drive motors 412, 422 to driveaccordingly along the wall.

In some examples, as shown in FIG. 12B, the robot 100 includes a contactelement 180 (e.g., a roller, bearing, bushing, or soft contact point)disposed at one or both of the front corners of the robot 100 to aidwall following. Preferably, the contact element 180 is at least disposedon the front corner of the dominant side of the robot 100. As the robot100 moves along the wall, it contacts the will with the contact element180, instead of merely scraping along the wall. In some implementations,the contact element 180 is a side brush that notes along a vertical axisand extends beyond the body 300. The side brush maintains a buffer spacebetween a wall and the robot body 300.

The bump sensor 800 is used to determine when the robot 100 hasphysically encountered an object. Such sensors may use a physicalproperty such as capacitance or physical displacement within the robot100 to determine when it has encountered an obstacle. In someimplementations, the bump sensor 800 includes contract sensors disposedabout the periphery of the body 300. In preferred implementations, thebump sensor 800 is configured to detect movement of the body 300 overthe chassis 200. Referring to FIGS. 5, 10 and 13A-13D, the body 300 ofthe robot 100 functions as a bumper and is flexibly coupled to thechassis 200 by one or more elastic elements 309 (e.g., springs, flexiblepins, elastomeric pegs, etc) (see FIG. 5). The elastic elements 309allow the bumper style body 300 to move in at least two directions(preferably three directions). In some examples, the bump sensor 800includes a bump sensor base 810 carrying at least three (preferablyfour) detectors 820 (e.g., light or infrared light detectors, such as aphoto-detector) equally spaced on the bump sensor base 810. In theexample shown, the bump sensor base 810 is a printed circuit boardcarrying the detectors 820. The printed circuit board—bump sensor base810 is in communication with and may carry the controller 450. The bumpsensor 800 includes a bump sensor shroud 830 defining a cavity 832 thatis positioned over and covering the bump sensor base 810. The bumpsensor shroud 830 houses an emitter 840 (e.g., light or infrared lightemitter), which emits a signal 842 (e.g., light) through an orifice 834defined by the bump sensor shroud 830 through a wall 836 of the cavity832. The orifice 834 collimates the signal 842, so as to have a directedpath. As the bump sensor shroud 830 moves over the bump sensor base 810,the signal 842 moves over the detectors 820, which provide correspondingsignals to the controller 450 (e.g., proportional to signal intensity).Based on the detector signals, the controller 450 is configured todetermine the direction of movement of the body 300 over the chassis200, and optionally the rate of movement. The bump sensor 800 may detect360 degrees of movement of the bump sensor shroud 830 over the bumpsensor base 810. The drive system 400 and/or the controller 450 areconfigured to alter a drive direction of the robot 100 in response tothe detector signal(s) received from the detectors 820.

In the example shown in FIGS. 13A and 13C, the bump sensor 800 includesa bumper guide 850 that guides the body 300 along two directions ofmovement. As noted above, the body 300 is coupled to the chassis byelastic elements 309 that allow the body 300 to be displaces both bytranslation and rotation. The bumper guide 850 may be configured as a“T”, cross shaped, or orthogonal groove(s) 852 formed in a member thatmoves with the bumper 300 (relative to the chassis 300), mated to atleast one guide pin 854 on the chassis 200 that doesn't move (relativeto the chassis 200). In other implementations, the bumper guide 850 isdefined in a portion of the chassis 200 and the guide pin 854 is securedto the bumper body 300. When the bumper 300 is displaced, bumper guide850 tends to guide the bumper 300 in that area along an arm of thebumper guide 850, which permits “translate” bumps as is and tends tootherwise reduce rotational components or guide rotation intotranslation, improving the detection of the bump sensor 800.

In the examples shown in FIGS. 5, 10 and 13D, the bump sensor 800includes a bumper connector arm 850 secured between the bump sensorshroud 830 and the bumper style body 300. The bumper connector arm 850translates movement of the body 300 to the bump sensor shroud 830. Thebump sensor shroud 830 can be secured to the bump sensor base 710 and becomprised of an elastic material such that the bump sensor shroud 830can move by elastic deflection in relation to the bump sensor base 810.

In other examples, the bump sensor shroud 830 is positioned over thebump sensor base 710 and allowed to move freely in relation to the bumpsensor base 810.

The robot 100 has a forward drive direction and carries theomni-directional receiver 900 on an upper portion 305 of the body 300above the forward portion 202 of the chassis 200. FIG. 1 illustrates anexample position of the omni-directional receiver 900 on the robot 100,as being the highest part of the robot 100. The omni-directionalreceiver 900 may be used to sense when the robot 100 is in closeproximity to a navigation beacon (not shown). For example, theomni-directional receiver 900 may relay a signal to a control systemthat indicates the strength of an emission, where a stronger signalindicates closer proximity to a navigation beacon.

FIGS. 14-16 show perspective, side, and cut-away views of theomni-directional receiver 900. The omni-directional receiver 900includes a housing 910, a conical reflector 920 and an emission receiver930. The housing 910 has an upper portion 912 and an inner cavity 916.The upper portion 912 may allow a transmission of an emission into theinner cavity 916. The conical reflector 920 is located on an uppersurface of the cavity 916 to reflect emissions falling on the upperportion 912 of the housing 910 into the inner cavity 916. The emissionreceiver 930 is located in the inner cavity 916 below the conicalreflector 920. In some implementations, the omni-directional receiver900 is configured to receive transmissions of infrared light (IR). Insuch cases, a guide 940 (e.g., a light pipe) may guide emissionsreflected off the conical reflector 920 and channel them to the emissionreceiver 930.

The controller 450 may be configured to propel the robot 100 accordingto a heading setting and a speed setting. Signals received from thenavigational sensor system 700 may be used by a control system to issuecommands that deal with obstacles, such as changing the commanded speedor heading of the robot 100. For instance, a signal from the proximitysensor 730 due to a nearby wall may result in the control system issuinga command to slow down. In another instance, a collision signal from thebump sensor 800 due to an encounter with an obstacle may cause thecontrol system to issue a command to change heading. In other instances,the speed setting of the robot 100 may be reduced in response to thecontact sensor and/or the heading setting of the robot 100 may bealtered in response to the proximity sensor 730.

The controller 450 may include a first independent behavioral routineconfigured to adjust the speed setting of the robot 100; and a secondindependent behavioral routine configured to alter the heading settingof the robot 100, in which the first and second independent behavioralroutines are configured to execute concurrently and mutuallyindependently. The first independent behavioral routine may beconfigured to poll the proximity sensor 730, and the second independentbehavioral routine may be configured to poll the bump sensor 800. Whileimplementations of the robot 100 discussed herein may use behavioralbased control only in part or not at all, behavior based control iseffective at controlling the robot to be robust (i.e. not getting stuckor failing) as well as safe.

FIGS. 17-25 illustrate another implementation of the autonomous coveragerobot 101. The robot 101 includes a chassis 200 having a forward portion210 and a rearward portion 220 and a body 300 having a forward portion301 and a rearward portion 303 configured to substantially follow thecontours of the chassis 200. The forward portion 210 of the chassis 200defines a substantially rectangular shape and the rearward portion 220defines an elliptical shape. The forward portion 301 of the body 300 maybe flexibly connected to the chassis 200. A handle 330 is disposed on ordefined by an upper portion 305 of the rearward portion 303 of the body300.

In an example configuration, the form factor of the robot 101 is about15 cm in diameter, about 7.5 cm in height, and functions on batterypower to clean for about six hours before requiring recharge. Also, forexample, the robot 101 may effectively clean the floor of a singleaverage-size room in about 45 minutes, or several smaller areas.

Referring to FIGS. 18, 20 and 21, the robot 101 includes a drive system400 carried by the chassis 200, as described above. In theimplementation shown, the drive motors 412, 422 are disposed adjacentand in-line (e.g., co-axial) with their respective drive wheels 410 and420. In some examples, the robot includes a gear box 414, 424 coupledbetween the drive wheel 410, 420 and its respective drive motor 412,422. The robot 101 includes a controller 450 in communication with thedrive system 400. The controller 450 is configured to maneuver the robot101 to pivot in place.

The robot 101 includes a cleaning assembly 500 mounted on the frontportion 210 of the chassis 200 includes a first, front roller brush 510rotatably mounted substantially near and substantially parallel to thefront edge 202 of the chassis 200. The cleaning assembly 500 includessecond and third side roller brushes 550, 560 rotatably mountedorthogonally to the front roller brush 510 substantially near respectiveright and left side edges 306, 308 of the body 300. The roller brushes510, 550, 560 are driven by a cleaning motor 530 coupled to the rollerbrushes 510, 550, 560 by a gear box 532. The cleaning motor 530 ispositioned rearward of the front roller brush 510 and between the sideroller brushes 550, 560.

The robot 101, in a preferred implementation, includes only one kind ofcleaning mechanism. For example, the robot 101 shown in FIG. 18 includesbristle-brush rollers for the front roller brush 510 and side rollerbrushes 550, 560. The bristle-brush rollers may be similar to the brushrollers found in the SCOOBA® robot marketed by iRobot Corporation, forexample; or it may be similar to the R2 or R3 brush types used in theROOMBA® robot, as further examples. In one implementation, the brushdoes not pick up long hairs or fibers that would tend to become tightlywrapped around the brush, in order to minimize the frequency ofmaintenance required by the user for removing debris from the brush.Alternatively, the robot 101 may include two or more varieties ofcleaning mechanism, such as both a vacuum and bristle brushes, interalia.

In the some examples, the front roller brush 510 and the side rollerbrushes 550, 560, each rotate about a horizontal axis parallel to thework surface, thereby providing a horizontal cleaning assembly 500,although the main work width of the coverage robot 100 may includevertically rotating brushes, no brushes in lieu of a vacuum, areciprocating brush, a circulating belt member, and other known cleaningimplements. Each roller brush 510, 520, 550, 560 may have a cylindricalbody that defines a longitudinal axis of rotation. Bristles are attachedradially to the cylindrical body, and, in some examples, flexible flapsare attached longitudinally along the cylindrical body. As the rollerbrush 510, 520, 550, 560 rotates, the bristles and the flexible flapsmove debris on the work surface, directing it toward the bin 610 in therobot 100. In examples including a vacuum unit, the brushes 510, 520,550, 560 may also direct debris or dirt toward a suction path under thecleaning robot 100. In the case of a wet cleaning robot, the brushes510, 520, 550, 560 may have instead a scrubbing function, and a vacuumor other collector may collect waste fluid after scrubbing.

In the examples shown, the effective components of the cleaning assembly500 such as the brushes 510, 550, 560 are disposed toward the extremefront corners of the forward portion 210 of the chassis 200. As aresult, the area of floor that the rectangular forward portion 210 ofthe chassis 200 can cover is maximized, and portions of the floor thatare not covered are minimized, as illustrated in FIG. 27.

By including only a single cleaning mechanism, such as the cleaningassembly 500, rather than a combination of two or more varieties ofcleaning mechanisms (such as, for example, both a roller brush and avacuum; or both wet and dry cleaning mechanisms, which may necessitatetwo or more storage chambers, inter alia), the robot 101 may be mademore compact relative to otherwise.

Referring to FIGS. 18, 20, 21 and 24, the robot 101 includes a binassembly 600, as described above. In the examples shown, the chassis 200defines the debris chamber or bin 610, which is positioned between thecleaning assembly 500 and the drive system 400. In specific examples,the bin 610 is forward of the drive wheels 410, 420 and rearward of thefront roller brush 510. As the front roller brush 510 and the sideroller brushes 550, 560 spin against the floor, they agitate debris andsweep the debris into a debris chamber/bin 610 within the robot 101 viaan intake slot or other suitable opening leading from the roller brushes510, 550, 560 to the debris chamber 610.

The bin cover 620, in the example shown, is releasably connected to thechassis 200 by one or more hinges 622 (e.g., living hinge, peg andsocket, etc.). In some implementations, the bin-cover release 630 isactuatable from substantially near or at the handle 330, therebyallowing actuation of the bin-cover release 630 while holding the handle330. In other implementations, the bin-cover release 630 is actuatablenear or on the bin cover 620, such that a user holds the handle 330 withone hand and opens the bin cover 620 via the bin-cover release 630 withanother hand (see FIG. 24). In some implementations, the bin coverrelease 630 is a spring biased latch or latching button attractable bypressing downwardly (e.g., button) or pulling upwardly (e.g., trigger).

In the examples shown, the robot 101 includes a handle 330 is disposedon or defined by an upper portion 305 of the body 300. A user can graspthe handle 330 to lift the robot 101 and transport it manually. Inaddition, the robot 101 may include one or more buttons 632 proximal tothe handle 330. The button 632 is preferably operable by one hand, whilethe user's hand grips the robot 101 by the handle 330. The button 632 isconfigured to actuate a bin-cover release 630, which is operable tocontrol holding the bin cover 620 in its closed position and releasingthe bin cover 620 to move to its open position. In one example, asillustrated in FIG. 24, when the user operates the button 632, thebin-cover release 630 disengages and the bin cover 620 swings open aboutthe hinges 622. With the bin cover 620 in its open position, thecontents of the debris chamber/bin 610 can drop out of the robot 101under the force of gravity. The robot 101 may also include a spring toensure that the bin cover 620 opens in case the weight of the debris inthe debris chamber 610 is insufficient to swing the bin cover 620 open,for example.

The robot 101 includes a power source 160 (e.g., battery) incommunication with the drive system 400 and/or the controller 450, andremovably secured to the chassis 200. In the examples shown in FIGS. 20and 21, the power source 160 is received by a power receptacle 260defined by the rearward portion 220 of the chassis 200. A power cover262 is releasably secured to the chassis 200 to hold and/or cover thepower source 160 in the power receptacle 260. In the examples shown, thepower source 160 is positioned in the rearward portion 220 of thechassis 200, rearward of the drive wheels 410, 420. In this position,the weight of the power source 160 offsets the weight of the cleaningassembly 500 to position a center of gravity of the robot 101substantially about a center of the chassis 200.

The compact dimensions of the robot 101 allow the robot 101 to navigateunder potential obstacles such as chairs, tables, sofas, or otherhousehold objects, and perform floor cleaning in these hard-to-reachareas. In addition, the robot 101 may include a clearance sensordisposed on a top surface thereof, such as a sonar range-finder orlight-sensitive diode, that scans directly overhead. When the clearancesensor detects the presence of an object within a thresholddistance—such as, for example, two feet—the robot 101 may continuemoving until the overhead space is clear. Accordingly, the robot 101 mayavoid becoming “lost” underneath furniture, out of view of the user, forexample.

As the drive system 400 propels the robot 101 over the floor, the frontroller brush 510 preferably rotates in the same direction as the drivewheels 410, 420 but at a rate faster than the rate of the robot 101traversing over the floor, so as to sweep debris into the debris chamber610. In addition, the side brushes 550, 560 also sweep debris inward atthe same time. In one example, the bristles of the brushes 510, 550, 560may extend downward by about 0.015 to 0.025 inches beyond the extent ofthe wheels 410, 420, while rotating at between about 600 and about 1600RPM.

The form factor of the robot 101 may be made more compact by omitting acaster wheel or other support structure. Due to the width of the frontbrush roller 510, as well as the side brushes 550, 560 disposed atopposite lateral sides of the robot 101, the robot 101 may omit a thirdcaster or free wheel aside from the drive wheels 410, 420 withoutsignificantly impacting the balance or stability of the robot 101.Alternatively, the robot 101 may further include support bearings 490,as shown in FIGS. 18, 20, and 22-25, disposed proximal to the extremeopposite corners of the forward portion 210 of the chassis 200. Thesupport bearings 490 may include a single rigid member of a smoothand/or self-lubricating material, such as polytetrafluoroethylene or apolyoxymethylene polymer; or, the support bearings 490 may include aroller bearing or any other suitable mechanism for preventing the robot101 from tipping or losing balance while providing a low frictionalresistance as the robot 101 traverses the floor.

Referring to FIG. 21, the robot 101 includes a navigational sensorsystem 700 in communication with the controller 450 that allows therobot 101 to be aware of its surroundings/environment and react inprescribed manners or behaviors according to its sensed perception ofits surroundings/environment. In the example shown, the navigationalsensor system 700 includes one or more bump sensors 800 and/or a stasisdetector 720. Using input from the navigational sensor system 700, thecontroller 450 generates commands to be carried out by the robot 101. Asa result, the robot 101 is capable of cleaning surfaces in an autonomousfashion.

The bump sensor 800 is used to determine when the robot 100 hasphysically encountered an object. Such sensors may use a physicalproperty such as capacitance or physical displacement within the robot100 to determine when it has encountered an obstacle. In the exampleshown in FIG. 21, the bump sensor 800 is a contract switch disposedabout the periphery of the front portion 210 of the chassis 200, betweenthe chassis 200 and the forward portion 301 of the body 300. The forwardportion 301of the body 300 is flexibly or slidably attached to thechassis 200 in a manner that allows contact with an obstacle to betranslated to the bump sensor(s) 800. In preferred implementations, therobot includes bump sensors 800 disposed at the forward corners of thechassis 200, with at least one bump sensor 800 disposed on each side ofeach corner, thus allowing the robot 100 to determine a direction and/orlocation of a collision. The forward portion 301 of the body 300 acts asa single mechanical bumper with sensors 800 substantially at the twoends of the bumper for sensing movement of the bumper. When the forwardportion 301 of the body 300 is compressed, the timing between the sensorevents is used to calculate the approximate angle at which the robot 101contacted the obstacle. When the forward portion 301 of the body 300 iscompressed from the right side, the right bump sensor detects the bumpfirst, followed by the left bump sensor, due to the compliance of thebumper and the bump detector geometry. This way, the bump angle can beapproximated with only two bump sensors.

Since the robot 101 preferably has a compact and lightweight form, themomentum carried by the robot 101 may be lighter than a standard-sizerobot. Accordingly, the robot 101 preferably includes “light touch” orcontactless bump sensors. For example, the robot 101 may include one ormore accelerometers 458 in communication with the controller 450 (seeFIG. 21) for monitoring the robot's acceleration along at least onehorizontal axis. When acceleration is detected that exceeds apre-established threshold, the robot 101 may respond as though a bumperswitch had been triggered. As a result, the robot 101 may omit atraditional contact-switch type bump sensor.

In some examples, the robot 101 may utilize the accelerometer 458 as astasis detector 720. As a benefit, processing accelerometer data forstasis detection may require only a processing rate of about 30 hertz.For example, as the robot 101 is moving over a floor, vibrations causethe accelerometer 458 to detect acceleration of a particular amplitudeprofile. However, when the robot 101 stops moving, because of either anormal state or it has been blocked by an obstacle, the amplitude of thevibrations detected by the accelerometer 458 decrease accordingly.Therefore, the robot 101 can respond to such decreased accelerationaccording to a stasis-escape behavior, for example. By monitoring asingle accelerometer 458 for purposes of both bump detection and/orstasis detection, the robot 101 may omit bump switches and/or otherstasis detection hardware, thus potentially requiring less space aboardthe robot 101.

Referring to FIGS. 26-28, the robot 100, 101 can navigate over floorsurfaces such as tile, hardwood or carpeting, while collecting debrisfrom the floor within the debris chamber/bin 610. When the robot 100,101 navigates into a corner, the front roller brush 510 and the endbrushes 540 or the side roller brushes 550, 560, respectively, caneffectively clean an area that is flush up against the sides of thecorner. In comparison, a round-outline robot 10, such as illustrated inFIG. 28, can approach a corner 9220 but cannot move flush against thewalls 9241, 9242 intersecting at the corner 9220. As a result, theround-outline robot 10 cannot effectively clean the wedge-shaped area9290 abutting the corner 9290. As illustrated in FIG. 26, the robot 100,101 can navigate along a straight path while remaining substantiallyflush against a wall edge 9210 where a wall 9421 intersects the floor9250. The robot 100, 101 preferably includes one or more bump sensors800, 1800 disposed or active within the front portion 210 of the chassis200; and as the robot 100, 101 taps against the wall 9241, the robot100, 101 can adjust its heading so as to travel substantially parallelto the wall 9241, for example.

The operation of the robot 101 is preferably controlled by amicrocontroller 450, such as a FREESCALE™ QG8 or other microcontrollersuitable to receive input from the robot's sensors and operate themotors or other output devices of the robot 101. As illustrated in FIGS.29-32, for example, the microcontroller 450 receives input from bumpsensor 800 and outputs control signals to the drive motors 412, 422coupled to the right and left drive wheels 410, 420. Alternatively, amicroprocessor or other control circuitry may be used. The robot 101 mayexecute behavior-based control software; or may operate according tosimple, single-threaded control loops, inter alia.

The rectangular outline of the front portion 210 of the chassis 200 maycause the corners thereof to collide with obstacles which might not bedetected by bump sensors or cliff sensors, in contrast to round-outlinerobots that can rotate freely without such risk, the robot 101preferably responds to bumps detected while rotating in place by haltingthe rotation and backing up directly in reverse. As a result, the robot101 may be less likely to become inextricably wedged or stuck,notwithstanding the square corners of the front portion 210 of thechassis 200. Alternatively, the robot 101 may behave in accordance withcontrol software generally similar to the ROOMBA™ or SCOOBA™ robots, asexamples.

In accordance with a further example, the robot 100, 101 mayautomatically return to a cradle or base station for storage aftercompleting a cleaning cycle. The robot 100, 101 may also include anelectrical interface for recharging on-board batteries. Additionally,the cradle or base station may include a receptacle positioned below a“home” position of the robot 100, 101. When the robot 100, 101interfaces the cradle and stops at the home position, the robot 100, 101may automatically actuate the bin-cover release 630 and evacuate thedebris from the debris chamber 610 into the cradle's receptaclepositioned below the robot 100, 101.

In robot implementations using the omni-directional receiver 900, thebase station may include an omni-directional beam emitter and twonavigational field emitters. The robot 100 may maneuver towards basestation by detecting and advancing along one of the lateral field edgesof the overlapping fields aligned with a docking direction until dockedwith the base station. The robot 100 may detect the emissions of basestation with the omni-directional receiver 900 and maneuver to detect anouter lateral field edge of at least one field emission. The robot 100may then advance along the outer lateral field edge to the alignedlateral field edge of the overlapping fields. Upon detecting the alignedlateral field edge, the robot 100 advances along the aligned lateralfield edge until docked with base station.

FIG. 33 is a block diagram showing a behavioral software architecturewithin the controller 450. The behavioral software architecture includesgoal-oriented behaviors. The robot 100, 101 employs a control andsoftware architecture that has a number of behaviors that are executedby an arbiter 1005 in the controller 450. The arbiter 1005 executescommands on motor drives 1010 in communicates with each drive motor 412,422. A behavior is entered into the arbiter 1005 in response to a sensorevent. In one implementation, all behaviors have a fixed relativepriority with respect to one another. The arbiter 1005 (in this case)recognizes enabling conditions, which behaviors have a full set ofenabling conditions, and selects the behavior having the highestpriority among those that have fulfilled enabling conditions. Thediagram shown in FIG. 33 does not necessarily reflect the (fixed)priority hierarchy of the robot 100, 101. In order of decreasingpriority, the behaviors are generally categorized as escape and/oravoidance behaviors (such as avoiding a cliff or escaping a corner) andworking behaviors (e.g., wall following, bouncing, or driving in astraight line). Movement of the robot 100, 101, if any, occurs while abehavior is arbitrated. If more than one behavior is in the arbiter1005, the behavior with a higher priority is executed, as long as anycorresponding required conditions are met. For example, a cliff avoidingbehavior 1400 will not be executed unless a cliff has been detected by acliff detection sensor, but execution of the cliff avoiding behavior1400 always takes precedence over the execution of other behaviors thatalso have satisfied enabling conditions.

The reactive behaviors have, as their enabling conditions or triggers,various sensors and detections of phenomena, but, in general, not(arbitrary) states of a sequence. As shown in FIG. 33, these includesensors for obstacle avoidance and detection, such as cliff sensors 710,stasis detector 720, side proximity sensor 730, bump sensor 800, and/oran omni-directional receiver 900 (e.g., for detection of a virtual wallsignal (which may instead be considered a coverage trigger)). Sensors ofthese types are monitored and conditioned by filters, conditioning, andtheir drivers, which can generate the enabling conditions as well asrecord data that helps the behavior act predictably and on all availableinformation (e.g., conversion to one-bit “true/false” signals, recordingof likely angle of impact or incidence based on strength or timedifferences from a group of sensors, or historical, averaging,frequency, or variance information).

Actual physical sensors may be represented in the architecture by“virtual” sensors synthesized from the conditioning and drivers.Additional “virtual” sensors that are synthesized from detectable orinterpreted physical properties, proprioceptive or interpreted upon therobot 100, 101, such as over-current of a motor, stasis or stuckcondition of the robot 100, 101, battery charge state via coulometry,and other virtual sensors “virtual N.”

In some implementations, the robot 100 includes the following behaviorslisted in priority order from high to low: 1) User Interface Group 1100,2) Factory Test Group 1200, 3) Reverse Bump Follow Group 1300, 4) CliffAvoid Group 1400, 5) Bounce Rear 1500, 6) Bump Follow Group 1600, 7)Bounce 1700, and 8) Drive 1800. A behavior group refers to a set ofbehaviors that work together to implement an overall behavior. Forexample, the “User Interface Group” behavior is a set of three behaviorsthat handles the user interface while the robot is at rest.

The robot may include a user interface 370, which is a singleclean/power button in the examples shown in FIGS. 1 and 17, for allowinga user to interact with the robot 100. The following sub-behaviors ofthe User Interface Group behavior 1100, prioritized from high to low,execute the user interface 370 implemented as a single clean/powerbutton: 1) User Off 1110, 2) User Start 1120, and 3) User Do Nothing1130. The following sub-behaviors of the Factory Test Group behavior1200, prioritized from high to low, implement a factory test mode forquality control purposes: 1) Factory Test Complete 1210, 2) Factory TestAdvance 1220, and 3) Factory Test 1230.

The following sub-behaviors, prioritized from high to low, implement theReverse Bump Follow escape behavior 1300: 1) Reverse Bump Follow EscapeSwing 1310, 2) Reverse Bump Follow Turn Out 1320, and 3) Reverse BumpFollow Arc In 1330. Due to the rectangular shape of the front portion210 of the chassis 200, it is possible for the robot 100 to drive into aspace that is too narrow to turn around in (e.g., like a parking space).These confinement areas are referred to as canyons. The term “canyon”refers generically to any narrow confinement source. If a cliff issimilarly confining the robot 100 to a narrow space, this is referred toas a plank. Since the strategy for escaping these confinement obstaclesis the same, the directional cliff sensor and bumper sensor data isaggregated into a set of four “directional confinement” sensors whichare the basis for the discussion below. The four sensors are front-left,front-right, rear-left and rear-right. The direction of a reverse bumpfollow is clockwise if the Reverse Bump Follow Arc In behavior 1330 isdriving the robot 100 backward while rotating clockwise. The directionof a reverse bump follow is counterclockwise if the Reverse Bump FollowArc In behavior 1330 is driving the robot 100 backward while rotatingcounterclockwise.

The Reverse Bump Follow Escape Swing behavior 1310 causes the robot 100to turn in place with enough angular progress to deduce that thepresence of a canyon. The activation condition for the Reverse BumpFollow Escape Swing behavior 1310 is evaluated at the end of the ReverseBump Follow Turn Out behavior 1320. After the Reverse Bump Follow EscapeSwing behavior 1310 is armed, it executes once and then disables itselfuntil armed again by the Reverse Bump Follow Turn Out behavior 1320. Atthe start of the Reverse Bump Follow Escape Swing behavior 1310, anescape angle is set to a random number between 120 and 160 degrees. Therobot 100 then turns in place in the opposite direction of the reversebump follow direction until the escape angle is achieved. If any reardirectional confinement sources appear while turning in place, the robot100 moves forward to avoid them. If a front directional confinementsource is encountered, the turn in place is aborted. After completion ofthe turn in place, the success of the escape is determined in thefollowing order. First, if the turn in place was aborted due todetection of a front confinement source, the angular progress of theturn in place is compared to a minimum escape angle which is computed bygenerating a random number between 80 and 120 degrees. If the angularprogress does not exceed this amount, a similar maneuver for the ReverseBump Follow Turn Out behavior 1320 is performed. This is done to returnthe robot 100 back to an orientation conducive to continuing the reversebump follow. Second, if the turn in place was aborted due to detectionof a front confinement source, and the angular progress exceeded theminimum escape angle computed above but fell short of the escape anglecomputed at the beginning of the behavior, the following is done. Thereverse bump follow activation is cancelled, and a forward bump followis triggered if the confinement source that stopped the turn in placewas a bump. This improves the chances that the robot 100 will find itsway out of a tight spot without detecting a new canyon and retriggeringthe reverse bump follow. Third, if the turn in place completed due toachieving the escape angle computed at the start of the behavior, thereverse bump follow activation is cancelled.

The Reverse Bump Follow Turn Out behavior 1320 attempts to orient therobot 100 relative to an obstacle such that forward progress can be madewhile arcing toward the obstacle again. Simply turning in place as acircular robot would is not sufficient for the robot 100 since therectangular forward portion 210 of the chassis 200 would, at some point,hit the obstacle and prevent the robot 100 from turning in placefurther. To avoid this problem, the robot 100 instead follows a tightarc to maintain space from the obstacle. The Reverse Bump Follow TurnOut behavior 1320 begins after the backing up along an arc that isperformed in the Reverse Bump Follow Arc In behavior 1330 finishes as aresult of the rear bumper getting activated. The first task of theReverse Bump Follow Turn Out behavior 1320 is to release the bumper 300from the rear hit. This is done by driving the robot 100 forward untilthe bumper 300 is released. In the course of doing this, frontconfinement sources are handled in the following way. A front-leftconfinement source causes the robot 100 to turn clockwise. A front-rightconfinement source causes the robot 100 to turn counterclockwise. Afterthe bumper 300 is released, the robot 100 computes a constrained randomarc radius and angular progress that it must travel in the forwarddirection in order to reorient the robot 100 for the next iteration ofthe Reverse Bump Follow Arc In behavior 1330. The robot 100 travelsalong this arc until the computed angular progress is achieved. Whiledoing this, the robot 100 responds to the front confinement sensor 710,730, 800 (e.g., cliff sensor 710, proximity sensor 730, and/or bumpsensor 800) on the opposite side of the robot 100 to the obstacle beingfollowed. When this is detected, the robot 100 turns in place in thesame rotational direction as the arc it is following. The Reverse BumpFollow Turn Out behavior 1320 ends when the computed angular progress isachieved or the front confinement sensor 710, 730, 800 on the same sideof the robot 100 as the obstacle being followed is triggered. At the endof the behavior, a random number generator is used to decide whether ornot to trigger a Reverse Bump Follow Escape Swing behavior 1310. At aminimum, the probability of triggering the Reverse Bump Follow EscapeSwing behavior 1310 will be about 20%. If the angular progress of theReverse Bump Follow Turn Out behavior 1320 was between about 2 and about5 degrees, the probability increases to about 50%. If the angularprogress is less than 2 degrees, the probability is about 100%.

The Reverse Bump Follow Arc In behavior 1330 attempts to make forwardprogress while keeping an obstacle close to one side of the robot 100 bydriving backward in an arc that begins shallow and gets progressivelymore severe with elapsed time in the behavior. The Reverse Bump FollowArc In behavior 1330 executes when the robot 100 is in the reverse bumpfollowing mode 1300 and none of the other reverse bump follow behaviors1310, 1320 are activated. While traveling in the arc, the robot 100 willrespond to the front confinement sensor 710, 730, 800 (e.g., cliffsensor 710, proximity sensor 730, and/or bump sensor 800) on theopposite side of the robot 100 to the obstacle. It does this by turningin place in the opposite rotational direction to the arc being followed.The Reverse Bump Follow Arc In behavior 1330 ends when a rearconfinement sensor 710, 800 (e.g., cliff sensor 710 and/or bump sensor800) is triggered or the arc has made over 120 degrees of angularprogress.

The Cliff Avoid Group behavior 1400 is a group of escape behaviors thatincludes the following sub-behaviors, prioritized from high to low: 1)Cliff Avoid Rear 1410, and 2) Cliff Avoid 1420. Referring to FIG. 4, inpreferred implementations, the robot 100 has four cliff sensors 710positioned at the front-right, front-left, rear-right and rear-leftextremes of the robot 100. The front-right and front-left cliff sensors710A, 710B detect when the either of the respective front corners of therobot 100 move over a cliff. Since the drive system 400 is positionedrearward of the cleaning assembly 500, which is located near the frontedge, the robot 100 can back-up before an appreciably amount of therobot 100 moves over the cliff edge. The rear-right and rear-left cliffsensors 710C, 710D are positioned directly rearward of the respectiveright and left drive wheels 410, 420. As a result, the rear-right andrear-left cliff sensors 710C, 710D detect when a rearward portion of therobot 100 moves over a cliff edge before the drive wheels 410, 420 moveover the cliff edge, so as to prevent driving in reverse at angle off ofa cliff. If the robot 100 included rear cliff sensors 710 only along acenter portion of the rearward portion 220 of the chassis 200, the robot100 could drive in reverse at an angle and move a drive wheel 410, 420over a cliff edge before detecting the cliff edge.

The CliffAvoid Rear behavior 1410 executes whenever the rear cliffsensors 710C, 710D are triggered. Front cliffs sensors 710A, 710B arealso handled in this behavior 1410 since it is higher priority thanCliffAvoid 1420. At the beginning of the Cliff Avoid Rear behavior 1410,an escape direction of clockwise or counterclockwise is selected. Thedecision is made in the following order. 1) If front-left cliff sensor710B is triggered, set to clockwise. 2) If front-right cliff sensor 710Ais triggered, set to counterclockwise. 3) If rear-right cliff sensor710C is triggered, set to clockwise. 4) If rear-left cliff sensor 710Dis triggered, set to counterclockwise. After the direction is set, therobot 100 turns in the specified direction along an arc that is centeredon a drive wheel 410, 420. While traveling, the front cliff sensors 710are monitored and used to alter the direction of travel as follows. Ifthe front-right cliff sensor 710A is triggered, the robot 100 turns inplace counterclockwise. If the front-left cliff sensor 710B istriggered, the robot 100 turns in place clockwise. The robot 100continues to travel as described above until both rear cliff sensors710C, 710D are not triggering.

The Cliff Avoid behavior 1420 only handles the front cliff sensors 710A,710B of the robot 100 and typically executes when the robot 100 isdriving forward. At the beginning of the Cliff Avoid behavior 1420, anescape direction is chosen based on which front cliff sensors 710A, 710Bhave been triggered. If only the front-left cliff sensor 710B istriggered, the clockwise escape direction is chosen. If only thefront-right cliff sensor 710A is triggered, counterclockwise escapedirection is chosen. If both front cliff sensors 710A, 710B aretriggered, the escape direction is randomly selected. An escape angle israndomly chosen between about 25 and about 50 degrees. The Cliff Avoidbehavior 1420 starts by backing up straight until both of the frontcliff sensors 710A, 710B are not triggering. Then, the robot 100 turnsin place until the escape angle is achieved. If any of the front cliffsensor 710A, 710B is retriggered as part of the turn in place, theentire Cliff Avoid behavior 1420 is retriggered and hence re-executed.

The Bounce Rear behavior 1500 runs when the bumper 300 is activated fromthe rear direction. This most commonly happens when the robot 100 drivesbackward to release the front part of the bumper 300 as part of theBounce behavior 1700. The robot 100 drives forward until the bumper 300is released, and then continues forward another 5 mm in order to reducethe chance that the turn in place about to be performed will notretrigger a rear bump. A rotational direction for the turn in place isdecided based on the direction of the original rear bumper hit. If thehit came from the rear-right side of the robot 100, counterclockwise ischosen. If the hit came from the rear-left side of the robot 100,clockwise is chosen. If the hit was in the center part of the rear, thedirection is randomly chosen. An escape angle is randomly chosen betweenabout 10 degrees and about 200 degrees. The robot 100 turns in thechosen direction until the escape angle is achieved.

The Bump Follow Group 1600 includes the following sub-behaviorsprioritized from high to low: 1. Bump Follow Wall Align 1610, 2. BumpFollow Arc In 1620. Bump following is used to escape from and cleancluttered areas. It is also used to follow a wall with the goal ofdispersing the robot 100 evenly through its floor space.

The Bump Follow Wall Align behavior 1610 is designed to align the sideof the robot 100 with an obstacle such as a wall. If thebump-follow-direction is clockwise, the goal is to have the robot's leftside against the wall. If the direction is counterclockwise, the goal isto have the robot's right side against the wall. When bump following isenabled, the Bump Follow Wall Align behavior 1610 begins when a frontbump is triggered. The location of the bumper hit is used to decide howmuch the robot 100 should turn in place before performing anotheriteration of the Bump Follow Arc In behavior 1620. If the bumper 300 istriggered on the side of the bumper 300 that should not be near theobstacle, the robot 100 sets a turn in place goal of between about 25and about 45 degrees. This larger increment saves time in the alignmentprocess. If the bumper 300 is triggered on the side that should be nearthe obstacle, the robot 100 turns in place in the direction that swingsthe bumper 300 into the obstacle even more. The goal of this maneuver isto see if the bumper 300 tends to stay engaged or releases. If itreleases, it suggests that the robot 100 is not yet at a very shallowangle to the wall, and a turn in place goal of between about 5 and about25 degrees is selected. Otherwise, the robot 100 is probably at ashallow angle to the wall, and a turn in place goal of between about 1and about 5 degrees is selected. If the turn in place goal was selectedto be greater than 5 degrees, the robot 100 backs up until the bumper300 is released. The robot 100 turns in place in the direction thatswings the front of the robot 100 away from the obstacle until thetarget angle is achieved. If the bumper 300 is retriggered during theturn in place, the robot 100 backs up enough to release it.

The Bump Follow Arc In behavior 1620 runs when the bump following mode1600 is enabled and Bump Follow Wall Align 1610 is not active. The robot100 drives forward in a shallow arc, at first, in order to make forwardprogress. As more time elapses, the arc gradually tightens to bring therobot 100 back in contact with the obstacle. This allows the obstacle tobe followed closely which can help the robot 100 find its way around it.If the bump follow mode 1600 was selected to maneuver through clutter,the robot 100 can continue arcing in without a bumper hit for up toabout 100 degrees of angular progress. At that point, the bump follow1600 is considered ended due to the robot escaping. If the bump followmode 1600 was selected to help disperse the robot 100 through its space,it can continue arcing in without a bumper hit for up to about 210degrees to allow for turning wall corners. At that point, the wall isconsidered lost and the bump follow behavior 1600 ends.

The Bounce behavior 1700 runs when the bumper 300 is activated from thefront direction. The robot 100 drives backward until the bumper 300 isreleased. It then continues backward another 30 mm in order to reducethe chance that the turn in place about to be performed will notretrigger the bumper 300 from the front. This large additional clearanceis required due to the rectangular shape of the forward portion of thebumper 300 creating the potential for the corner of the bumper 300 toswing into contact with the obstacle when turning in place. A rotationaldirection for the turn in place is decided based on the direction of theoriginal front hit on the bumper 300. If the hit came from thefront-right side of the robot 100, counterclockwise is chosen. If thehit came from the front-left side of the robot 100, clockwise is chosen.If the hit was in the center part of the front, the direction israndomly chosen. An escape angle is randomly chosen between about 10degrees and about 200 degrees. The robot 100 turns in the chosendirection until the escape angle is achieved.

The drive behavior 1800 may run when no other behavior is active. Therobot 100 drives straight until it experiences an event that triggersanother behavior.

The robot 100 maintains concurrent processes 2000, “parallel” processesthat are not generally considered reactive behaviors. As noted, filtersand conditioning 2400 and drivers 2500, can interpret and translate rawsignals. These processes are not considered reactive behaviors, andexercise no direct control over the motor drives or other actuators.

Some parallel processes 2000 are important in assisting the activationand execution of various behaviors. These processes are software finitestate machines that are evaluated at a frequency of 64 Hertz, forexample. The period is referred to as the processing interval.

In some implementations, the robot 100 includes a Canyon Detect process2100, which assists in identifying canyons. A canyon is declared bymonitoring four signals. Each of these signals is evaluated everyprocessing interval. When the input signal is true, the output signalbecomes true. The output signal becomes false after 100 consecutiveprocessing intervals of the input signal being false. The four inputsignals are evaluated as follows: 1) The front-left cliff sensor 710B isactive and the front-right cliff sensor 710A is inactive, or therear-left cliff sensor 710D is active and the rear-right cliff sensor710C is inactive. 2) The front-right cliff sensor 710A is active and thefront-left cliff sensor 710B is inactive, or the rear-right cliff sensor710C is active and the rear-left cliff sensor 710D is inactive. 3) Thebumper 300 is depressed at the front-left side of the robot 100. 4) Thebumper 300 is depressed at the front-right side of the robot 100. Theprocessed versions of these signals are named, respectively, asfollows: 1) cliff-left-held; 2) cliff-right-held; 3) bump-left-held; and4) bump-right-held. A canyon is detected when cliff-left-held orbump-left-held are true while cliff-right-held or bump-right-held aretrue. When a canyon is detected, the Reverse Bump Following Group 1300is enabled.

In some implementations, the robot 100 includes a Forward Progressprocess 2200. In the Forward Progress process 2200, every processinginterval, the forward progress of the robot 100 is added to anaccumulator while a fixed distance quantity corresponding to 1millimeter is subtracted. When this accumulator reaches 100 millimeters,forward progress is declared to be true. The accumulator is not allowedto exceed 200 millimeters. When forward progress is true for 10 seconds,the Reverse Bump Following Group 1300 is enabled to escape theexcessively cluttered environment the robot 100 is traveling in.

In some implementations, the robot 100 includes a Reverse Bump FollowArc In Progress process 2300. While the robot 100 is in the reverse bumpfollowing mode 1300, the forward progress of each iteration of theReverse Bump Follow Arc In behavior 1330 is fed into a low pass filter.At the beginning of a reverse bump follow, this filter is initialized to60 millimeters. When the output falls below 50 millimeters, the arc inprogress is considered poor. This triggers a toggle in the reverse bumpfollow direction, i.e. the side of the robot 100 where the primaryobstacle is assumed to be.

Other robot details and features combinable with those described hereinmay be found in the following U.S. patent applications filedconcurrently herewith, entitled “AUTONOMOUS COVERAGE ROBOT” havingassigned Ser. No. ______; and “AUTONOMOUS COVERAGE ROBOT SENSING” havingassigned Ser. No. ______; the entire contents of the aforementionedapplications are hereby incorporated by reference.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. Accordingly, otherimplementations are within the scope of the following claims.

1. An autonomous coverage robot comprising: a chassis having forward andrearward portions, the forward portion of the chassis defining asubstantially rectangular shape; a drive system carried by the chassisand configured to maneuver the robot over a cleaning surface; a cleaningassembly mounted on the forward portion of the chassis; a bin disposedadjacent the cleaning assembly and configured to receive debris agitatedby the cleaning assembly; a bin cover pivotally attached to a lowerportion of the chassis and configured to rotate between a first, closedposition providing closure of an opening defined by the bin and asecond, open position providing access to the bin opening; a bodyattached to the chassis; a handle disposed on an upper portion of thebody; and a bin cover release configured to control movement of the bincover between its first and second positions, the bin cover releasebeing actuatable from substantially near the handle.
 2. The autonomouscoverage robot of claim 1, wherein the bin cover release is configuredto move between a first, locking position which locks the bin cover inits first, closed position and a second, disengaged position whichallows the bin cover to move to its second, open position.
 3. Theautonomous coverage robot of claim 2, wherein the bin cover releasecomprises a spring biased latch.
 4. The autonomous coverage robot ofclaim 3, wherein the bin cover release further comprises a buttondisposed on the handle and configured to actuate the latch, therebyallowing actuation of the bin cover release while holding the handle. 5.The autonomous coverage robot of claim 1, wherein the cleaning assemblycomprises a first roller brush rotatably mounted substantially near afront edge of the chassis.
 6. The autonomous coverage robot of claim 5,wherein the cleaning assembly comprises a second roller brush rotatablymounted substantially parallel to and rearward of the first rollerbrush, the first and second roller brushes rotate in oppositedirections.
 7. The autonomous coverage robot of claim 6, wherein the binis disposed rearward of the first and second roller brushes and forwardof the drive system.
 8. The autonomous coverage robot of claim 6,wherein each roller brush comprises right and left end brushes extendingfrom respective ends of the roller brush beyond a lateral extend of thebody, each end brush extending at angle φ of between 0° and about 90°from a longitudinal axis defined by the roller brush.
 9. The autonomouscoverage robot of claim 1, wherein the cleaning assembly comprises afront roller brush rotatably mounted substantially near the front edgeof the chassis, and right and left side roller brushes rotatably mountedorthogonal to the front brush substantially near the respective rightand left side edges of the chassis.
 10. The autonomous coverage robot ofclaim 9, wherein the bin is disposed rearward of the front roller brushand substantially between the right and left side roller brushes andforward of the drive system.
 11. The autonomous coverage robot of claim1, wherein the rearward portion of the chassis defines an arcuate shape.12. The autonomous coverage robot of claim 1, wherein the drive systemcomprises right and left differentially driven drive wheels rotatablymounted to the rearward portion of the chassis, the drive system beingcapable of maneuvering the robot to pivot in place.
 13. The autonomouscoverage robot of claim 12, wherein the rearward portion of the chassisdefines a substantially semi-circular shape and the axes of the rightand left drive wheels are disposed on or rearward of a center axisdefined by the rearward portion of the chassis.
 14. The autonomouscoverage robot of claim 1, wherein the chassis and the body togetherhave a length of less than 23 cm and a width of less than 19 cm.
 15. Theautonomous coverage robot of claim 1, further comprising at least oneproximity sensor carried by a dominant side of the robot, the at leastone proximity sensor responsive to an obstacle substantially near thebody, the controller configured to alter a drive direction in responseto a signal received from the at least one proximity sensor.
 16. Theautonomous coverage robot of claim 1, further comprising at least onecliff sensor carried by a forward portion of the body and arrangedsubstantially near a front edge of the body, the at least one cliffsensor responsive to a potential cliff forward of the robot, the drivesystem configured to alter a drive direction in response to a signalreceived from the cliff sensor indicating a potential cliff.
 17. Theautonomous coverage robot of claim 1, further comprising at least onecliff sensor carried by a rearward portion of the body and arrangedsubstantially near the rear edge of the body, the at least one cliffsensor responsive to a potential cliff rearward of the robot, the drivesystem configured to alter a drive direction in response to a signalreceived from the cliff sensor indicating a potential cliff.
 18. Theautonomous coverage robot of claim 1, further comprising an idler wheeldisposed on the bin cover.
 19. The autonomous coverage robot of claim18, wherein the rearward portion of the chassis defines a substantiallysemi-circular shape and the idler wheel is position at least ⅓ theradius of the substantially semi-circular shaped rearward portionforward of the drive wheels.
 20. The autonomous coverage robot of claim18, wherein the idler wheel comprises a stasis detector comprising: amagnet disposed in or on the idler wheel; and a magnet detector disposedadjacent the idler wheel for detecting the magnet as the idler wheelrotates.
 21. An autonomous coverage robot comprising: a chassis havingforward and rearward portions; a drive system carried by the rearwardportion of the chassis and configured to maneuver the robot over acleaning surface; a controller in communication with the drive system,the controller configured to maneuver the robot to pivot in place; acleaning assembly mounted on the forward portion of the chassis; a bumpsensor in communication with the controller and configured to detectmovement in multiple directions; and a body flexibly attached to thechassis and substantially covering the chassis, wherein contact with thebody is translated to the bump sensor for detection; wherein thecontroller is configured to alter a drive direction of the robot inresponse to a signal received from the bump sensor; and wherein the bumpsensor comprises: a sensor base; a sensor shroud positioned adjacent thesensor base and connected to the body; an emitter housed by the sensorshroud, the emitter emitting a signal onto the sensor base; and at leastthree detectors carried by the sensor base and configured to detect theemitted signal; wherein movement of the sensor shroud causes movement ofthe emitted signal over the detectors.
 22. The autonomous coverage robotof claim 21, wherein the bump sensor detects 360 degrees of movement ofthe body about the bump sensor.
 23. The autonomous coverage robot ofclaim 21, wherein the bump sensor comprises four detectors arranged in arectangular configuration with respect to each other.
 24. The autonomouscoverage robot of claim 21, wherein the sensor shroud defines an orificethrough which the emitter emits its signal onto the sensor base.
 25. Theautonomous coverage robot of claim 24, wherein the emitter comprises aninfrared light emitter and the detectors comprise infrared lightdetectors, the orifice collimating the emitted signal onto the sensorbase.
 26. The autonomous coverage robot of claim 1, further comprising abumper guide configured to confine body movements to along twodirections.
 27. The autonomous coverage robot of claim 26, wherein thebumper guide comprises two orthogonal grooves defined by the body andconfigured to receive a guide pin disposed on the chassis.
 28. Theautonomous coverage robot of claim 1, wherein the cleaning assemblycomprises a first roller brush rotatably mounted substantially near afront edge of the chassis.
 29. The autonomous coverage robot of claim28, wherein the cleaning assembly comprises a second roller brushrotatably mounted substantially parallel to and rearward of the firstroller brush, the first and second roller brushes rotate in oppositedirections.
 30. The autonomous coverage robot of claim 29, furthercomprising a bin disposed rearward of the first and second rollerbrushes and forward of the drive system, the bin configured to receivedebris agitated by the cleaning assembly.
 31. The autonomous coveragerobot of claim 29, wherein each roller brush comprises right and leftend brushes extending from respective ends of the roller brush beyond alateral extend of the body, each end brush extending at angle φ ofbetween 0° and about 90° from a longitudinal axis defined by the rollerbrush.
 32. The autonomous coverage robot of claim 21, wherein thecleaning assembly comprises a front roller brush rotatably mountedsubstantially near the front edge of the chassis, and right and leftside roller brushes rotatably mounted orthogonal to the front brushsubstantially near the respective right and left side edges of thechassis.
 33. The autonomous coverage robot of claim 32, furthercomprising a bin disposed rearward of the front roller brush andsubstantially between the right and left side roller brushes and forwardof the drive system, the bin configured to receive debris agitated bythe cleaning assembly.
 34. The autonomous coverage robot of claim 21,wherein, the forward portion defining a substantially rectangular shapeand the rearward portion of the chassis defines an arcuate shape. 35.The autonomous coverage robot of claim 21, wherein the drive systemcomprises right and left differentially driven drive wheels rotatablymounted to the rearward portion of the chassis, the drive system beingcapable of maneuvering the robot to pivot in place.
 36. The autonomouscoverage robot of claim 21, further comprising at least one proximitysensor carried by a dominant side of the robot, the at least oneproximity sensor responsive to an obstacle substantially near the body,the controller configured to alter a drive direction in response to asignal received from the at least one proximity sensor.
 37. Theautonomous coverage robot of claim 21, further comprising at least onecliff sensor carried by a forward portion of the body and arrangedsubstantially near a front edge of the body, the at least one cliffsensor responsive to a potential cliff forward of the robot, the drivesystem configured to alter a drive direction in response to a signalreceived from the cliff sensor indicating a potential cliff.
 38. Theautonomous coverage robot of claim 21, further comprising at least onecliff sensor carried by a rearward portion of the body and arrangedsubstantially near the rear edge of the body, the at least one cliffsensor responsive to a potential cliff rearward of the robot, the drivesystem configured to alter a drive direction in response to a signalreceived from the cliff sensor indicating a potential cliff.
 39. Anautonomous coverage robot comprising: a chassis having forward andrearward portions, the forward portion defining a substantiallyrectangular shape and the rearward portion defining an arcuate shape; adrive system carried by the rearward portion of the chassis andconfigured to maneuver the robot over a cleaning surface, the drivesystem comprising right and left drive wheels differentially driven bycorresponding right and left motors; a controller in communication withthe drive system, the controller configured to maneuver the robot topivot in place; a cleaning assembly mounted on the forward portion ofthe chassis; an accelerometer in communication with the controller, thecontroller controlling the drive system in response to a signal receivedfrom the accelerometer.
 40. The autonomous coverage robot of claim 39,wherein the controller alters a drive direction of the robot in responseto a signal received from the accelerometer indicating an abrupt speedchange.
 41. The autonomous coverage robot of claim 39, wherein thecontroller alters a drive direction of the robot in response to a signalreceived from the accelerometer indicating stasis of the robot.
 42. Theautonomous coverage robot of claim 39, wherein the controller reduces adrive speed of the robot in response to a signal received from theaccelerometer indicating a maximum speed.
 43. The autonomous coveragerobot of claim 42, wherein the maximum speed is between about 200 mm/sand about 400 mm/s.
 44. The autonomous coverage robot of claim 39,wherein the cleaning assembly comprises a first roller brush rotatablymounted substantially near a front edge of the chassis.
 45. Theautonomous coverage robot of claim 44, wherein the cleaning assemblycomprises a second roller brush rotatably mounted substantially parallelto and rearward of the first roller brush, the first and second rollerbrushes rotate in opposite directions.
 46. The autonomous coverage robotof claim 45, further comprising a bin disposed rearward of the first andsecond roller brushes and forward of the drive system, the binconfigured to receive debris agitated by the cleaning assembly.
 47. Theautonomous coverage robot of claim 45, wherein each roller brushcomprises right and left end brushes extending from respective ends ofthe roller brush beyond a lateral extend of the body, each end brushextending at angle φ of between 0° and about 90° from a longitudinalaxis defined by the roller brush.
 48. The autonomous coverage robot ofclaim 39, wherein the cleaning assembly comprises a front roller brushrotatably mounted substantially near the front edge of the chassis, andright and left side roller brushes rotatably mounted orthogonal to thefront brush substantially near the respective right and left side edgesof the chassis.
 49. The autonomous coverage robot of claim 48, furthercomprising a bin disposed rearward of the front roller brush andsubstantially between the right and left side roller brushes and forwardof the drive system, the bin configured to receive debris agitated bythe cleaning assembly.
 50. The autonomous coverage robot of claim 49,wherein the chassis and the body together have a length of less than 23cm and a width of less than 19 cm.
 51. The autonomous coverage robot ofclaim 39, further comprising at least one proximity sensor carried by adominant side of the robot, the at least one proximity sensor responsiveto an obstacle substantially near the body, the controller configured toalter a drive direction in response to a signal received from the atleast one proximity sensor.
 52. The autonomous coverage robot of claim39, further comprising at least one cliff sensor carried by a forwardportion of the body and arranged substantially near a front edge of thebody, the at least one cliff sensor responsive to a potential cliffforward of the robot, the drive system configured to alter a drivedirection in response to a signal received from the cliff sensorindicating a potential cliff.
 53. The autonomous coverage robot of claim39, further comprising at least one cliff sensor carried by a rearwardportion of the body and arranged substantially near the rear edge of thebody, the at least one cliff sensor responsive to a potential cliffrearward of the robot, the drive system configured to alter a drivedirection in response to a signal received from the cliff sensorindicating a potential cliff.
 54. An autonomous coverage robotcomprising: a chassis having forward and rearward portions, the forwardportion defining a substantially rectangular shape, the rearward portiondefining an arcuate shape; a drive system carried by the rearwardportion of the chassis and configured to maneuver the robot over acleaning surface, the drive system comprising right and left drivewheels differentially driven by corresponding right and left motors; acontroller in communication with the drive system, the controllerconfigured to maneuver the robot to pivot in place; a cleaning assemblymounted on the forward portion of the chassis, the cleaning assemblycomprising: a first roller brush rotatably mounted substantially near afront edge of the chassis; and a second roller brush rotatably mountedsubstantially parallel to and rearward of the first roller brush, thefirst and second roller brushes rotating in opposite directions; a bindisposed rearward of the cleaning assembly and configured to receivedebris agitated by the cleaning assembly; a bin cover pivotally attachedto a lower portion of the chassis and configured to rotate between afirst, closed position providing closure of an opening defined by thebin and a second, open position providing access to the bin opening; abin cover release configured to control movement of the bin coverbetween its first and second positions; a handle disposed on thechassis, wherein the bin cover release is actuatable from substantiallynear the handle; a body flexibly attached to the chassis andsubstantially covering the chassis, the body being movable in relationto the handle and the chassis; and a bump sensor in communication withthe controller and configured to detect movement in multiple directions,wherein contact with the body is translated to the bump sensor fordetection; wherein the controller is configured to alter a drivedirection of the robot in response to a signal received from the bumpsensor.
 55. The autonomous coverage robot of claim 54, wherein the bumpsensor comprises: a sensor base; a sensor shroud position adjacent thesensor base and connected to the body; an emitter housed by the sensorshroud, the emitter emitting a signal onto the sensor base; and at leastthree detectors carried by the sensor base and configured to detect theemitted signal; wherein movement of the sensor shroud causes movement ofthe emitted signal over the detectors.
 56. The autonomous coverage robotof claim 54, further comprising a bumper guide configured to confinebody movements to along two directions.
 57. The autonomous coveragerobot of claim 56, wherein the bumper guide comprises two orthogonalgrooves defined by the body and configured to receive a guide pindisposed on the chassis.
 58. The autonomous coverage robot of claim 54,wherein the chassis and the body together have a length of less than 23cm and a width of less than 19 cm.
 59. The autonomous coverage robot ofclaim 58, wherein the drive wheels are disposed less than 9 cm rearwardof the cleaning assembly.
 60. The autonomous coverage robot of claim 54,further comprising an idler wheel disposed on the bin cover.
 61. Theautonomous coverage robot of claim 60, wherein the rearward portion ofthe chassis defines a substantially semi-circular shape and the idlerwheel is position at least ⅓ the radius of the substantiallysemi-circular shaped rearward portion forward of the drive wheels. 62.The autonomous coverage robot of claim 54, further comprising a powersource disposed in the rearward portion of the chassis substantiallybetween the right and left wheels.
 63. The autonomous coverage robot ofclaim 62, wherein the power source is disposed adjacent and rearward ofthe bin.
 64. The autonomous coverage robot of claim 54, wherein thecleaning assembly further comprises a brush motor configured to drivethe first and second roller brushes, the brush motor being disposedsubstantially near a forward edge of the chassis.
 65. The autonomouscoverage robot of claim 54, wherein the first roller brush is disposedsubstantially near a forward edge of the chassis.
 66. The autonomouscoverage robot of claim 54, further comprising at least one proximitysensor carried by a dominant side of the robot, the at least oneproximity sensor responsive to an obstacle substantially near the body,the controller configured to alter a drive direction in response to asignal received from the at least one proximity sensor.
 67. Theautonomous coverage robot of claim 54, further comprising at least onecliff sensor carried by a forward portion of the body and arrangedsubstantially near a front edge of the body, the at least one cliffsensor responsive to a potential cliff forward of the robot, the drivesystem configured to alter a drive direction in response to a signalreceived from the cliff sensor indicating a potential cliff.
 68. Theautonomous coverage robot of claim 67, further comprising right and leftfront cliff sensors disposed at the respective right and left corners ofa forward portion of the robot.
 69. The autonomous coverage robot ofclaim 54, further comprising at least one cliff sensor carried by arearward portion of the body and arranged substantially near the rearedge of the body, the at least one cliff sensor responsive to apotential cliff rearward of the robot, the drive system configured toalter a drive direction in response to a signal received from the cliffsensor indicating a potential cliff.
 70. The autonomous coverage robotof claim 69, further comprising right and left rear cliff sensorsdisposed directly rearward of the respective right and left drivewheels.